api: remove ::dummy from Id types

`::dummy` was used for testing purposes and became redundant after
adding e.g. `from_raw` and `into_raw` methods on `Id` types.

src/platform_impl/web/event_loop/mod.rs

@@ -1,4 +1,4 @@
-use super::{backend, event, window, HasMonitorPermissionFuture, MonitorPermissionFuture};
+use super::{backend, window, HasMonitorPermissionFuture, MonitorPermissionFuture};
 use crate::application::ApplicationHandler;
 use crate::error::{EventLoopError, NotSupportedError};
 use crate::event::Event;